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Proceedings Paper

Methods to protect and recover work function of air exposed transition metal oxide thin films
Author(s): Irfan Irfan; Chenggong Wang; Alexander James Turinske; Yongli Gao
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Paper Abstract

Insertion of high work function (WF) transition metal oxide (TMO) layers between the anode and the hole transport layer is established to substantially enhance the performance of organic light emitting diodes (OLED). The high WF of transition metal oxide layer has been demonstrated to be the most crucial for the enhancement. The WF of a TMO layer decreases substantially with air exposure, and noticeably by the ambient even inside a low vacuum system. In the present work we discuss various methods to protect and recover the high WF after a TMO thin film has been exposed to air. We report covering a thin organic layer on top of MoOx to protect the high work function. We found that a thin layer of 1-2 nm organic layer was sufficient to protect the work function of MoOx thin film underneath. We further report methods to recover already decreased TMO WF due to air exposure. We performed oxygen plasma cleaning of air exposed MoOx film and found out that oxygen plasma could substantially recover the WF of as deposited MoOx film. We also performed annealing of air exposed MoOx film inside an ultra high vacuum system and observed a thin layer of oxygenrich adsorbate layer, which desorbed upon annealing that in turn substantially recovered the MoOx WF. We discuss the vacuum annealing and the effect of resulting surface on the interface energy level alignment.

Paper Details

Date Published: 13 September 2012
PDF: 5 pages
Proc. SPIE 8476, Organic Light Emitting Materials and Devices XVI, 847616 (13 September 2012); doi: 10.1117/12.927812
Show Author Affiliations
Irfan Irfan, Univ. of Rochester (United States)
Chenggong Wang, Univ. of Rochester (United States)
Alexander James Turinske, Univ. of Wisconsin (United States)
Yongli Gao, Univ. of Rochester (United States)
Central South Univ. (China)

Published in SPIE Proceedings Vol. 8476:
Organic Light Emitting Materials and Devices XVI
Franky So; Chihaya Adachi, Editor(s)

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